Disc brakes have been commonplace in automobiles for decades. Most modern cars have disc brakes on the front wheels, and often on all four wheels. Disc brakes generally include a rotor or disc connected to the wheel and/or axle, and a pair of brake pads on either side of the rotor that are squeezed inwardly against the rotor by means of a caliper. The caliper may be actuated, for example, hydraulically or pneumatically.
Brake pads generally include a metal backing plate with friction material fixed on one side to contact the rotor. Brake pads also typically have a shim, or noise insulator, on the opposite side of the backing plate from the friction material. Brake shims are thin metal, composite, rubber and/or adhesive pads that fit between the brake pad and the brake caliper to correct for differences that may lead to noise or rattling.
A brake shim may be attached to a backing plate by clip-on tabs that attach around edges of the back plate, by adhesive layer on the face of the shim, by riveting, or combinations thereof. Riveting is a common way to attach shims, particularly in shims for which tabs are impractical or undesired. An orbital riveting process is typically used in which distal ends of lugs, extending from the backing plate and through holes in the shim, are riveted and spread apart to secure the shim. However, one problem with this type of attachment is that the shim has a tendency to buckle or otherwise not lay flat if the holes do not correctly align with lugs, or if the lug swells during the riveting process.